Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$146.38	8.779%	$159.2307	$159.23	$159.25	$159.20
Purchase #2	$116.32	13.154%	$131.6207	$131.62	$131.60	$131.60
Purchase #3	$132.71	8.441%	$143.9121	$143.91	$143.90	$143.90
Purchase #4	$160.55	6.615%	$171.1704	$171.17	$171.15	$171.20
Purchase #5	$37.65	10.293%	$41.5253	$41.53	$41.55	$41.50
Purchase #6	$32.45	5.324%	$34.1776	$34.18	$34.20	$34.20
Purchase #7	$97.39	13.548%	$110.5844	$110.58	$110.60	$110.60
7 purchase totals =	$723.45		$792.2212	$792.22	$792.25	$792.20